CN110581951B

CN110581951B - Mouth cleaner and control method thereof

Info

Publication number: CN110581951B
Application number: CN201910780362.XA
Authority: CN
Inventors: 萧元昱; 刘劲廷
Original assignee: Qisda Optronics Suzhou Co Ltd; Qisda Corp
Current assignee: Qisda Optronics Suzhou Co Ltd; Qisda Corp
Priority date: 2019-08-22
Filing date: 2019-08-22
Publication date: 2021-12-14
Anticipated expiration: 2039-08-22
Also published as: US11992290B2; CN110581951A; US20210052163A1

Abstract

The invention provides a mouth-sweeping machine and a control method thereof, wherein the method comprises the following steps: after the first projection device finishes turning on the light, the second projection device is triggered to start turning on the light; the first projector sends out a first camera trigger signal when starting to turn on the lamp; the first delay circuit delays the first camera trigger signal until the second projection device finishes turning on the lamp; and when the first camera and the second camera receive the delayed first camera trigger signal, the first camera and the second camera start exposure. The invention can use a plurality of projectors and cameras to scan the oral cavity so as to identify the correct three-dimensional position information of the teeth, increases the scanning area by adding the projectors and the cameras, reduces the scanning time, and improves the scanning accuracy and the scanning efficiency of the oral scanner.

Description

Mouth cleaner and control method thereof

Technical Field

The invention relates to the technical field of optical scanning, in particular to a mouth-scanning machine and a control method thereof.

Background

The oral scanner uses laser to scan teeth quickly, and then uses software to build tooth model, providing medical personnel for simulation or other purposes. At present, the oral scanning machine only uses one projector and one camera to scan a plurality of teeth, resulting in a small scanning area and a slow scanning speed.

Therefore, there is a need to design a new oral cleaning machine and a control method thereof to overcome the above-mentioned drawbacks.

Disclosure of Invention

The invention aims to provide an oral scanner and a control method thereof, which can arrange a plurality of groups of projectors and cameras in the oral scanner to scan the oral cavity.

In order to achieve the above object, the present invention provides a control method of a mouth-sweeping machine, the method comprising: after the first projection device finishes turning on the light, the second projection device is triggered to start turning on the light; the first projector sends out a first camera trigger signal when starting to turn on the lamp; the first delay circuit delays the first camera trigger signal until the second projection device finishes turning on the lamp; and when the first camera and the second camera receive the delayed first camera trigger signal, the first camera and the second camera start to expose,

preferably, the step of triggering the second projection device to start turning on the light after the first projection device finishes turning on the light includes: after the first projection device finishes turning on the lamp, a first projection trigger signal is transmitted to the second projection device; and when the second projection device receives the first projection trigger signal, the second projection device starts to turn on the lamp.

Preferably, the first projection device needs a first time period from starting to finishing turning on the light; the second projection device needs a second time period from starting to turning on the lamp to finishing turning on the lamp; and the first delay circuit delays the first camera trigger signal for a time greater than the sum of the first time period and the second time period.

Preferably, the method further comprises: when the first camera and the second camera finish capturing images, the first projection device, the second projection device, the first camera and the second camera are closed; when the first projection device is turned off, triggering a third projection device to start up and turn on a lamp; after the third projection device finishes turning on the light, the fourth projection device is triggered to start turning on the light; the third projection device sends out a second camera trigger signal when the lamp is started and turned on; the second delay circuit delays the second camera trigger signal until the fourth projection device finishes turning on the lamp; and when the third camera and the fourth camera receive the delayed second camera trigger signal, the third camera and the fourth camera start exposure.

Preferably, the first predetermined pattern projected by the first projection device is interlaced with the third predetermined pattern projected by the third projection device, and the second predetermined pattern projected by the second projection device is interlaced with a fourth predetermined pattern projected by the fourth projection device.

In addition, the present invention also provides a mouth-sweeping machine, comprising: the first projection device is used for projecting; the second projection device is coupled to the first projection device and used for projection; a first delay circuit, coupled to the first projection device, for delaying a first camera trigger signal emitted by the first projection device; a first camera coupled to the first delay circuit for capturing an image; and a second camera, coupled to the first delay circuit, for capturing an image; when the first projection device finishes lighting, the second projection device is triggered to start lighting, when the first projection device starts lighting, a first camera trigger signal is sent out, the first delay circuit delays the first camera trigger signal until the second projection device finishes lighting, and when the first camera and the second camera receive the delayed first camera trigger signal, the first camera and the second camera start exposure.

Preferably, the mouth cleaner further comprises: an inverter coupled to the first projection device; a third projection device coupled to the inverter for projecting; a fourth projection device, coupled to the third projection device, for projecting; a second delay circuit, coupled to the third projection device, for delaying a second camera trigger signal emitted by the third projection device; a third camera coupled to the second delay circuit for capturing an image; and a fourth camera, coupled to the second delay circuit, for capturing an image; when the first projection device is turned off, the phase inverter triggers the third projection device to start up and turn on the light, the third projection device triggers the fourth projection device to start up and turn on the light after the light is turned on, the third projection device sends out the second camera trigger signal when the light is turned on, the second delay circuit delays the second camera trigger signal until the fourth projection device finishes turning on the light, and when the third camera and the fourth camera receive the delayed second camera trigger signal, the third camera and the fourth camera start exposure

Preferably, the first predetermined pattern projected by the first projection device is interlaced with the third predetermined pattern projected by the third projection device, and the second predetermined pattern projected by the second projection device is interlaced with the fourth predetermined pattern projected by the fourth projection device.

Preferably, the projection frequency of the first projection device is less than or equal to the reciprocal of the sum of the first time interval, the second time interval and the first camera exposure time interval.

Compared with the prior art, the oral scanner and the control method thereof can scan the oral cavity by using a plurality of projectors and cameras to identify correct three-dimensional position information of teeth.

Drawings

FIG. 1 is a block diagram of a mouth scanner according to an embodiment of the present invention;

FIG. 2 is a timing diagram of selected signals in the swipe machine according to an embodiment of the present invention;

FIG. 3 is a flowchart of a control method of the oral cleaning machine according to an embodiment of the present invention;

FIG. 4 is a block diagram of a mouth-cleaning machine according to another embodiment of the present invention;

FIG. 5 is a timing diagram of selected signals in the scan engine according to another embodiment of the present invention;

FIG. 6 is a flowchart illustrating a method for controlling a mouth cleaning machine according to another embodiment of the present invention;

FIG. 7 is a circuit diagram of a delay circuit in the scan circuit according to an embodiment of the present invention;

fig. 8 is a circuit diagram of an inverter circuit in the scan engine according to the embodiment of the present invention.

Detailed Description

In order to further understand the objects, structures, features and functions of the present invention, the following embodiments are described in detail.

Certain terms are used throughout the description and following claims to refer to particular components. As one of ordinary skill in the art will appreciate, manufacturers may refer to a component by different names. The present specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to.

Fig. 1 is a block diagram of a broom 1 according to an embodiment of the present invention. The oral scanner 1 can use two projection devices and two cameras to identify the three-dimensional position information of the object to be measured, and simultaneously increase the scanning area and reduce the scanning time.

The swipe machine 1 may include

projection devices

10, 12,

cameras

16, 18, and delay circuit 14. The projection device 10 may be coupled to the projection device 12 and the delay circuit 14. The delay circuit 14 may be coupled to the

cameras

16, 18, respectively. When the oral cavity scan machine 1 is in operation, the

projection devices

10 and 12 can respectively project the first portion and the second portion adjacent to each other in the predetermined pattern onto an object to be measured, such as a plurality of teeth. The

cameras

16, 18 can capture images of the first portion and the second portion of the predetermined pattern projected on the object to be tested, respectively. The projection device 10 can trigger the projection device 12 to project and synchronize the

cameras

16 and 18 to capture images, so as to ensure that the

projection devices

10 and 12 project the same predetermined pattern and that the

cameras

16 and 18 correctly capture the projected predetermined pattern. The predetermined pattern may be a structured light pattern, such as a checkered, striped, circular, cross pattern, gray scale coded pattern, color coded pattern, other coded pattern, or random pattern. The predetermined pattern is deformed when projected onto the surface of the object to be measured having different shapes, lines and/or depths, and the images captured by the

cameras

16, 18 may respectively display a first portion and a second portion of the deformed predetermined pattern. The oral scanner 1 can compare the images captured by the

cameras

16 and 18 with the original predetermined pattern to obtain the three-dimensional position information of the surface of the object.

Upon receiving the initialization signal Sini, the projection apparatus 10 may turn on the light and send a camera trigger signal Stric1 to the delay circuit 14. After the projector 10 is turned on, a projector trigger signal Strip1 may be transmitted to trigger the projector 12 to turn on the light. The delay circuit 14 may delay the camera trigger signal Stric1 until the projection device 12 completes turning on the light, and when the

cameras

16, 18 receive the delayed camera trigger signal Stric 1', the

cameras

16, 18 may start exposure. During projection, a first time period may be required from the start of the lamp by the projection apparatus 10 to the completion of the lamp, and a second time period may be required from the start of the lamp by the projection apparatus 12 to the completion of the lamp. When the projection apparatus 10 and the projection apparatus 12 are substantially the same, the length of the first period may be substantially equal to the length of the second period. The delay circuit 14 may delay the camera trigger signal Stric1 for a time greater than the sum of the first period and the second period. During image capture, the

cameras

16, 18 may require an exposure period to capture the first portion and the second portion of the projected predetermined pattern. When the

cameras

16 and 18 are substantially identical, the exposure periods required for the

cameras

16, 18 may be substantially identical. When the

cameras

16 and 18 are different, the required exposure period for the

cameras

16, 18 may be equal to the greater of the respective required exposure periods for the

cameras

16, 18.

Fig. 2 is a timing diagram of some selected signals used by the oral scanner 1, which may include the light on signals of the

projection devices

10, 12 and the exposure signals of the

cameras

16, 18. At time t1, the projector apparatus 10 receives the initial signal Sini, and the light-on signal of the projector apparatus 10 starts to climb. After a period of time X, at time t2, the projection device 10 finishes turning on the light and projecting the corresponding portion of the predetermined pattern, and transmits a projection device triggering signal Strip1 to trigger the projection device 12 to start turning on the light, so that the light-on signal of the projection device 12 starts to climb. The time X is greater than or equal to the first period of the projection apparatus 10. After a period of time Y, at time t3, the projection device 12 also completes turning on the light and projecting the corresponding portion of the predetermined pattern, and the

cameras

16, 18 begin exposure in response to the exposure signals from the

cameras

16, 18. The time Y is greater than or equal to the second period of the projection device 12. After a period of time Z, at time t4, the

cameras

16, 18 complete the exposure and capture the projected predetermined pattern, and the light-on signal of the projection apparatus 10, the light-on signal of the projection apparatus 12, and the exposure signals of the

cameras

16, 18 are reset to turn off the

projection apparatuses

10, 12 and the

cameras

16, 18. The time Z is greater than or equal to the exposure period of the

cameras

16, 18. The swipe machine 1 may require the sum of times X, Y, and Z to complete the projection and capture the predetermined pattern. In other words, the projection frequency of the

projection devices

10, 12 is less than or equal to the inverse of the sum of the first time period, the second time period, and the exposure time period of the

cameras

16, 18.

Fig. 3 shows a flow chart of a control method 3 of the oral cleaning machine 1. The control method 3 includes steps S300 to S308 for synchronizing the first group of

projection devices

10 and 12 for projection and the

cameras

16 and 18 for image capturing. Step S302 is used to trigger the projection apparatus 12 to start lighting, steps S300, S304, and S306 are used to synchronize image capturing of the

cameras

16 and 18, and step S308 is used to turn off the

projection apparatuses

10 and 12 and the

cameras

16 and 18. It should be noted that any reasonable technical changes or step adjustments fall within the scope of the present disclosure. Steps S300 to S308 are as follows:

step S300, when the projection device 10 starts to turn on the light, a camera trigger signal Stric1 is sent out;

step S302, after the projection device 10 finishes turning on the light, the projection device 12 is triggered to start the light;

step S304, the delay circuit 14 delays the camera trigger signal Stric1 until the projection apparatus 12 completes the light-on;

step S306, when the

cameras

16 and 18 receive the delayed camera trigger signal Stric 1', the

cameras

16 and 18 start exposure;

in step S308, after the

cameras

16 and 18 capture the images, the

projection devices

10 and 12 and the

cameras

16 and 18 are turned off.

The descriptions of steps S300 to S308 are already detailed in the foregoing, and will not be repeated herein. Through steps S300 to S308, the projection apparatus 10 can trigger the projection apparatus 12 to perform projection and synchronize the

cameras

16 and 18 to perform image capturing, so that the three-dimensional position information of the object to be measured can be correctly identified, and the scanning area can be increased and the scanning time can be reduced.

Preferably, the oral scanning device 1 is not limited to using only two projection devices and cameras, and more than two projection devices and cameras can be used. For example, when the oral scanner 1 uses three projectors and cameras, the projector 10 can still send out the projector trigger signal Strip1 to synchronize the other 2 projectors for projection after the lighting is turned on, and send out the camera trigger signal Strip1 to synchronize the image capture of 3 cameras when the lighting is turned on. The oral scanning device 1 and the control method 3 can trigger the projection device 12 to project and synchronize the

cameras

16 and 18 to capture images by the projection device 10, and can correctly identify the three-dimensional position information of the object without carrying a computing unit, and can increase the scanning area and reduce the scanning time.

Fig. 4 is a block diagram of the scan engine 4 according to another embodiment of the present invention, and the scan engine 4 may include

projection devices

10, 12, 40, 42,

cameras

16, 18, 46, 48,

delay circuits

14, 44, and an inverter circuit 49. The

projection devices

10, 12, 40, 42, the

cameras

16, 18, 46, 48 and the

delay circuits

14, 44 may be divided into two groups, and alternately perform operations of two groups of interleaved (interleaved) patterns with respect to the predetermined pattern. The

projection devices

10, 12, the

cameras

16, 18 and the delay circuit 14 may belong to a first group, and project and image a first group of interlaced patterns in the predetermined pattern; the

projection devices

40, 42, the

cameras

46, 48 and the delay circuit 44 may belong to a second group, projecting and imaging a second group of interlaced patterns in the predetermined pattern. The first set of interlaced patterns may include a first predetermined pattern and a second predetermined pattern, and the second set of interlaced patterns may include a third predetermined pattern and a fourth predetermined pattern. The first predetermined pattern is interlaced with the third predetermined pattern, and the second predetermined pattern is interlaced with the fourth predetermined pattern. The first and second sets may be coupled through an inverter circuit 49. The connection and operation of the

projection devices

10, 12, the

cameras

16, 18 and the delay circuit 14 in the oral scanner 4 are the same as those of the oral scanner 1, and will not be described herein again.

The projection apparatus 10 is coupled to the inverter circuit 49. The inverter circuit 49 is coupled to the projection device 40. The projection device 40 may be coupled to the projection device 42 and the delay circuit 44. The delay circuit 44 may be coupled to the

cameras

46, 48, respectively. The projection devices 10 of the first group can trigger the projection devices 40 of the second group to project through the phase inversion circuit 49. The projection device 40 can trigger the projection device 42 to project and synchronize the

cameras

46 and 48 to perform image capturing so as to synchronize the projection and image capturing of the third predetermined pattern and the fourth predetermined pattern. The

projection devices

40 and 42 can project a third predetermined pattern and a fourth predetermined pattern onto the object to be measured, respectively. The

cameras

46 and 48 can capture images of the third and fourth predetermined patterns projected on the object to be measured, respectively.

When the projection apparatus 10 is turned off, the projection apparatus 10 may send a trigger signal Stri2 to the inverter circuit 49, for example, to set a rising edge or a falling edge in the trigger signal Stri2 after the projection apparatus 10 is turned off. The inverter circuit 49 may generate an inverted trigger signal Stri 2', such as a falling edge or a rising edge in the trigger signal Stri2, to trigger the projection device 40 to start turning on the light. After the light is turned on, the projection device 40 triggers the projection device 42 to turn on the light. After receiving the inverted trigger signal Stri 2', the projector 40 can start turning on the light and send out the camera trigger signal Stric2 to the delay circuit 44, and the delay circuit 44 can delay the camera trigger signal Stric2 until the projector 42 finishes turning on the light. When the

camera

46, 48 receives the delayed camera trigger signal Stric 2', the

camera

46, 48 may begin exposure. During projection, a third time period may be required from the start of the lamp by the projection device 40 to the completion of the lamp, and a fourth time period may be required from the start of the lamp by the projection device 42 to the completion of the lamp. When the projection device 40 and the projection device 42 are substantially the same, the length of the third period may be substantially equal to the length of the fourth period. The delay circuit 44 may delay the camera trigger signal Stric2 for a time greater than the sum of the third time period and the fourth time period. During image capture, the

cameras

46 and 48 may need to perform exposure in an exposure period to capture the third and fourth predetermined patterns of the projection. When the

cameras

46 and 48 are substantially identical, the exposure periods required by the

cameras

46, 48 may be substantially identical. When the

cameras

46 and 48 are different, the required exposure period for the

cameras

46, 48 may be equal to the greater of the respective required exposure periods in the

cameras

46, 48.

Fig. 5 is a timing diagram of selected signals used by the swipe machine 4, including the light-on signals of the

projection devices

10, 12, 40, 42 and the exposure signals of the

cameras

16, 18, 46, 48. The timing of the light-on signals of the

projection devices

10 and 12 and the exposure signals of the

cameras

16 and 18 in fig. 5 is the same as that in fig. 2, and will not be described again. At time t4, the projection device 10 is turned off and the inverter circuit 49 may trigger the projection device 40 to turn on the light by inverting the trigger signal Stri 2'. When the projection apparatus 40 receives the inverted trigger signal Stri 2', the light-on signal of the projection apparatus 40 starts to climb. After a period of time X' at time t5, the projection device 40 finishes turning on the light and projecting the third preset pattern, and transmits the projection device triggering signal Strip2 to trigger the projection device 42 to start turning on the light, so that the light-on signal of the projection device 42 starts to climb. The time X' is greater than or equal to the third period of the projection device 40. After a period of time Y', at time t6, the projector 42 also completes lighting and projecting the fourth predetermined pattern, and the

cameras

46, 48 start exposure in response to the exposure signals of the

cameras

46, 48. The time Y' is greater than or equal to the fourth period of the projection device 42. After a period of time Z' at time t7, the

cameras

46 and 48 complete the exposure and capture the third and fourth predetermined patterns, and the light-on signal of the projection device 40, the light-on signal of the projection device 42, and the exposure signals of the

cameras

46 and 48 are reset to turn off the

projection devices

40 and 42 and the

cameras

46 and 48. The time Z' is greater than or equal to the exposure period of the

cameras

46, 48. The swipe 4 may require the sum of times X, Y, Z, X ', Y ', and Z ' to complete the projection and capture the predetermined pattern. In other words, the projection frequency of the

projection device

10, 12, 40, 42 is less than or equal to the inverse of the sum of the first, second, third, fourth periods and the exposure periods of the

camera

16, 18, 46, 48.

Fig. 6 shows a flow chart of a control method 6 of the oral cleaning machine 4. The control method 6 includes steps S600 to S620, wherein steps S600 to S606 are used for synchronizing the first set of

projection devices

10 and 12 for projection and the

cameras

16 and 18 for image capturing, step S608 is used for turning off the

projection devices

10 and 12 and the

cameras

16 and 18, steps S610 to S618 are used for synchronizing the second set of

projection devices

40 and 42 for projection and the

cameras

46 and 48 for image capturing, and step S620 is used for turning off the

projection devices

40 and 42 and the

cameras

46 and 48. It should be noted that any reasonable technical changes or step adjustments fall within the scope of the present disclosure. Steps S600 to S620 are as follows:

step S600, when the projection device 10 starts to turn on the light, a camera trigger signal Stric1 is sent out;

step S602, after the projection apparatus 10 finishes turning on the light, the projection apparatus 12 is triggered to start turning on the light;

step S604, the delay circuit 14 delays the camera trigger signal Stric1 until the projector 12 completes turning on the light;

step S606, when the

cameras

16 and 18 receive the delayed camera trigger signal Stric 1', the

cameras

16 and 18 start exposure;

step S608, turning off the

projection devices

10 and 12 and the

cameras

16 and 18 after the

cameras

16 and 18 complete capturing images;

step S610, when the projection device 10 is turned off, the inverter circuit 49 triggers the projection device 40 to start the lamp;

step S612, when the projection apparatus 40 starts to turn on the light, it sends out a camera trigger signal Stric 2;

step S614, after the projection device 40 finishes turning on the light, the projection device 42 is triggered to turn on the light;

in step S616, the delay circuit 44 delays the camera trigger signal Stric2 until the projector 42 completes the light-on;

step 618, when the

cameras

16 and 18 receive the delayed camera trigger signal Stric 1', the

cameras

16 and 18 start exposure;

in step S620, after the

cameras

46 and 48 complete capturing the images, the

projection devices

40 and 42 and the

cameras

46 and 48 are turned off.

The descriptions of steps S600 to S620 are already detailed in the foregoing, and will not be described herein again. By the steps S600 to S620, the projection apparatus 10 can control the first set of projection apparatus 12 to perform projection and image capturing by the

cameras

16 and 18 and the second set of

projection apparatus

40 and 42 to perform projection and image capturing by the

cameras

46 and 48, so that the three-dimensional position information of the object to be measured can be correctly identified without carrying a computing unit, and the scanning area can be increased and the scanning time can be reduced.

Preferably, the broom 4 is not limited to using only two sets of projection devices and cameras, and more than two sets of projection devices and cameras may be used. In some embodiments, when the mouth-broom 4 uses three sets of projection devices and cameras, the projection device 10 may be turned off after completing the projection and image capturing of the first set of projection device and camera and simultaneously trigger the projection and image capturing of the second set of projection device and camera, the projection device 40 may be turned off after completing the projection and image capturing of the second set of projection device and camera and simultaneously trigger the projection and image capturing of the third set of projection device and camera, and the first, second and third predetermined patterns projected and captured by the first, second and third sets of projection devices and cameras, respectively, may be interlaced.

Fig. 7 is a circuit diagram of the

delay circuit

14 or 44 in the

oral scanner

1 or 4. The

delay circuit

14 or 44 is implemented by a timer chip 70. The timer chip 70 may receive the trigger signal Sin and delay the trigger signal Sin for a delay time to generate a delayed trigger signal Sout. The length of the delay time is determined by the product of the resistance R of the resistor 72 and the capacitance C of the capacitor 74. In some embodiments, the time length T of the delay time may be 1.1 × R × C, i.e., after the time length T elapses after the trigger signal Sin is received, the timer chip 70 may generate the delayed trigger signal Sout.

Fig. 8 is a circuit diagram of the inverter circuit 49 in the scan circuit 4, wherein the inverter circuit 49 comprises a transistor 80,

resistors

82 and 84, a supply voltage terminal 86 and a common voltage terminal 88. The transistor 80 may be a Bipolar Junction Transistor (BJT) configured as a common emitter amplifier, which may include a control terminal, a first terminal, and a second terminal. The control terminal of transistor 80 receives input signal a through resistor 82. A first terminal of the transistor 80 may receive a supply voltage terminal 86 through the resistor 82 and output an inverted input signal a as an output signal OUT. The second terminal of the transistor 80 may be coupled to the common voltage terminal 88. The supply voltage terminal 86 may provide a supply voltage. The common voltage terminal 88 may provide a ground voltage.

In summary, the

scanners

1 and 4 and the

control methods

3 and 6 thereof use the projection device 10 of the

scanners

1 and 4 to synchronize other projection devices and cameras for projection and image capture, so that the three-dimensional position information of the object to be measured can be correctly identified without carrying a computing unit, and the scanning area can be increased and the scanning time can be reduced.

The present invention has been described in relation to the above embodiments, which are only exemplary of the implementation of the present invention. It should be noted that the disclosed embodiments do not limit the scope of the invention. Rather, it is intended that all such modifications and variations be included within the spirit and scope of this invention.

Claims

1. A control method of a mouth-cleaning machine is characterized by comprising the following steps:

after the first projection device finishes turning on the light, the second projection device is triggered to start turning on the light;

the first projector sends out a first camera trigger signal when starting to turn on the lamp;

the first delay circuit delays the first camera trigger signal until the second projection device finishes turning on the lamp; and

when the first camera and the second camera receive the delayed first camera trigger signal, the first camera and the second camera start exposure;

after the first projection device finishes turning on the lamp, a first projection trigger signal is transmitted to the second projection device; and

and when the second projection device receives the first projection trigger signal, the second projection device starts to turn on the lamp.

2. The method as claimed in claim 1, wherein the first period of time is required from the start of the lamp turning on to the completion of the lamp turning on of the first projector;

the second projection device needs a second time period from starting to turning on the lamp to finishing turning on the lamp; and

the first delay circuit delays the first camera trigger signal for a time greater than a sum of the first time period and the second time period.

3. The method for controlling a broom according to claim 1, further comprising:

when the first camera and the second camera finish capturing images, the first projection device, the second projection device, the first camera and the second camera are closed;

when the first projection device is turned off, triggering a third projection device to start up and turn on a lamp;

after the third projection device finishes turning on the light, the fourth projection device is triggered to start turning on the light;

the third projection device sends out a second camera trigger signal when the lamp is started and turned on;

the second delay circuit delays the second camera trigger signal until the fourth projection device finishes turning on the lamp; and

and when the third camera and the fourth camera receive the delayed second camera trigger signal, the third camera and the fourth camera start exposure.

4. The method as claimed in claim 3, wherein the first predetermined pattern projected by the first projection device is interlaced with the third predetermined pattern projected by the third projection device, and the second predetermined pattern projected by the second projection device is interlaced with a fourth predetermined pattern projected by the fourth projection device.

5. A mouth-sweeping machine is characterized in that the mouth-sweeping machine comprises:

the first projection device is used for projecting;

the second projection device is coupled to the first projection device and used for projection;

a first delay circuit, coupled to the first projection device, for delaying a first camera trigger signal emitted by the first projection device;

a first camera coupled to the first delay circuit for capturing an image; and

a second camera coupled to the first delay circuit for capturing an image;

when the first projection device finishes lighting, the second projection device is triggered to start lighting, when the first projection device starts lighting, a first camera trigger signal is sent out, the first delay circuit delays the first camera trigger signal until the second projection device finishes lighting, and when the first camera and the second camera receive the delayed first camera trigger signal, the first camera and the second camera start exposure.

6. The oral cleaning machine of claim 5, further comprising:

an inverter coupled to the first projection device;

a third projection device coupled to the inverter for projecting;

a fourth projection device, coupled to the third projection device, for projecting;

a second delay circuit, coupled to the third projection device, for delaying a second camera trigger signal emitted by the third projection device;

a third camera coupled to the second delay circuit for capturing an image; and

a fourth camera coupled to the second delay circuit for capturing an image;

when the first projection device is turned off, the phase inverter triggers the third projection device to start up the lamp, the third projection device triggers the fourth projection device to start up the lamp after the lamp is turned on, the third projection device sends out the second camera trigger signal when the lamp is turned on, the second delay circuit delays the second camera trigger signal until the fourth projection device finishes turning on the lamp, and when the third camera and the fourth camera receive the delayed second camera trigger signal, the third camera and the fourth camera start exposure.

7. The oral scanning device as claimed in claim 6, wherein the first predetermined pattern projected by the first projection device is interlaced with the third predetermined pattern projected by the third projection device, and the second predetermined pattern projected by the second projection device is interlaced with the fourth predetermined pattern projected by the fourth projection device.

8. The oral sweeper of claim 5, wherein the first projector requires a first period of time from the start of turning on the light to the completion of turning on the light;

9. The swipe engine of claim 8, wherein the projection frequency of the first projection device is less than or equal to the inverse of the sum of the first time period, the second time period and the first camera exposure time period.